Auckland(CNN) New Zealand Prime Minister Jacinda Ardern will return to the city of Christchurch on Wednesday for the second time since last week's deadly terror attacks at two mosques.
New Zealand is moving swiftly under Ardern's leadership to respond to what she called the "worst act of terrorism" in the Pacific island nation's history.
Ardern said on Monday that the attacks -- which killed 50 people and wounded dozens more -- exposed weaknesses in gun laws that the government will address through reforms to be announced within 10 days.
"There have rightly been questions about how this could have happened here," Ardern said Tuesday during her first address to Parliament since the attack.
"There is anger that it has happened here. There are questions that need to be answered and I assure you they will be."
Parliament members gathered in the House on Tuesday to share condolences for the victims. They will meet again on Wednesday, the same day Ardern intends to return to Christchurch.
Ardern said she will meet with first-responders and victims' families on Wednesday as they prepare for burials.
On Saturday, she visited members of Christchurch's Muslim community wearing a hijab in what observers lauded as a meaningful gesture of compassion and respect.
Speaking after her weekly cabinet meeting Monday evening, Ardern told reporters that ministers had agreed "in principle" to reform gun laws.
While acknowledging that "for a short period" the planned amendments might create uncertainty for some gun owners, Ardern said she believes "the vast majority" of New Zealand's gun owners agree that change is needed.
Earlier Monday, popular New Zealand e-commerce website TradeMe ended the sale of semi-automatic guns on its online marketplace.
"We have listened to public sentiment following Friday's terrorist attack in Christchurch and decided to remove all semi-automatic firearms sales and parts associated," TradeMe wrote in a statement.
The Prime Minister said an inquiry will look into the circumstances leading up to Friday's attack.
The inquiry will investigate what agencies knew -- or should have known -- about the gunman's access to weapons or any impediments into the sharing of information, she said. Those agencies include the New Zealand Security Intelligence Service, the Government Communications Security Bureau, police, customs and immigration, she said.
The inquiry will also look at the suspect's travel movements, activities in New Zealand, use of social media and contact with others.
Ardern said the government had preliminary discussions about giving New Zealanders an opportunity to commemorate the victims, but any national memorial service will not take place this week.
A quiet country reels after a horrific massacre
Ardern, accompanied by the governor-general, Patsy Reddy, and Parliament Speaker Trevor Mallard, on Monday opened a national condolence book for victims for people to sign in the National Library in Wellington.
"While it is a small action, the condolence book offers an opportunity for New Zealanders to unite and express our opposition to hate and state our commitment to the values of love and compassion," Ardern said.
Of the injured, 31 people remain in Christchurch Hospital, including nine in critical condition in intensive care, health officials said Monday. A 4-year-old girl also remains in a critical condition at a hospital in Auckland after being transferred there on Saturday. Her father is also in serious but stable condition in Auckland
New Zealand Police Commissioner Mike Bush told reporters Monday that the investigation into the attacks was the largest criminal probe ever undertaken by the country's police.
Australian Brenton Harris Tarrant, 28, is believed to be the only person responsible for the attacks, though he could have received support from others, the commissioner said.
Tarrant lived in the southern city of Dunedin, around 225 miles from Christchurch. Officials said he had no criminal history in New Zealand or Australia and had not drawn the attention of the intelligence community for extremist views.
Bush said the threat level in New Zealand remained high and there would be increased visibility from police and emergency service partners "for weeks to come."